Reading the data sheet is more useful than you think. The device will not output 12 volts with a 12 volt input. There is a minimum difference between the input voltage and the output voltage which is clearly stated.

If you overcome that problem, use the proper fixed resistor and a trim pot to set the output to 12 volts.

I admit it is not easy to spot the actual datasheet on that site and not just the basic numbers, but other than that you really need to read the datasheet of any part you want to use. Starting with maximum ratings, tips on how to use the part, test circuits, ending with footprint of that part. Everything you need is in there, you just need to read it.